U.S. patent application number 13/794589 was filed with the patent office on 2014-07-03 for iron-based composition for fuel element.
The applicant listed for this patent is Micah Hackett, Ronald Klueh. Invention is credited to Micah Hackett, Ronald Klueh.
Application Number | 20140182749 13/794589 |
Document ID | / |
Family ID | 51015789 |
Filed Date | 2014-07-03 |
United States Patent
Application |
20140182749 |
Kind Code |
A1 |
Hackett; Micah ; et
al. |
July 3, 2014 |
IRON-BASED COMPOSITION FOR FUEL ELEMENT
Abstract
Disclosed embodiments include fuel assemblies, fuel element,
cladding material, methods of making a fuel element, and methods of
using same.
Inventors: |
Hackett; Micah; (Bellevue,
WA) ; Klueh; Ronald; (Bellevue, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hackett; Micah
Klueh; Ronald |
Bellevue
Bellevue |
WA
WA |
US
US |
|
|
Family ID: |
51015789 |
Appl. No.: |
13/794589 |
Filed: |
March 11, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61747054 |
Dec 28, 2012 |
|
|
|
Current U.S.
Class: |
148/547 ;
148/622; 148/624 |
Current CPC
Class: |
C22C 38/002 20130101;
C21D 9/0068 20130101; C22C 38/44 20130101; C21D 2251/02 20130101;
C22C 38/02 20130101; C22C 38/001 20130101; C21D 6/02 20130101; C21D
2211/008 20130101; C22C 38/46 20130101; C22C 38/04 20130101; G21C
3/07 20130101; C21D 6/004 20130101; C22C 38/18 20130101; Y02E 30/30
20130101; C21D 6/008 20130101; C21D 2211/001 20130101; C21D 6/005
20130101 |
Class at
Publication: |
148/547 ;
148/622; 148/624 |
International
Class: |
C21D 6/02 20060101
C21D006/02 |
Claims
1. A method of making a composition, the method comprising: heat
treating a material including an iron-based composition at a first
temperature under a first condition in which at least some of the
iron-based composition is transformed into an austenite phase;
cooling the material to a second temperature at a cooling rate
under a second condition in which at least some of the iron-based
composition is transformed into a martensite phase; and heat
treating the material at a third temperature under a third
condition in which carbides are precipitated.
2. The method of claim 1, wherein the material is at least one of
cold rolled, cold drawn, and pilgered before the heat treating at
the first temperature.
3. The method of claim 1, wherein the iron-based composition
includes a steel.
4. The method of claim 1, wherein the iron-based composition
includes at least one element chosen from Cr, C, Mo, Ni, Mn, V, W,
Si, N, S, and P.
5. The method of claim 1, wherein heat treating at the first
temperature includes dissolving at least substantially all of
carbides, if any, present in the iron-based composition.
6. The method of claim 1, wherein the first temperature is between
about 1025.degree. C. and about 1100.degree. C.
7. The method of claim 1, wherein heat treating at the first
temperature includes heating the material to the first
temperature.
8. The method of claim 1, wherein heat treating at the first
temperature is carried out for at least 5 minutes.
9. The method of claim 1, wherein heat treating at the first
temperature is carried out for between about 5 minutes and about
120 minutes.
10. The method of claim 1, wherein substantially all of the
iron-based composition in heat treating at the first temperature is
transformed into an austenite phase.
11. The method of claim 1, wherein the second temperature is about
20.degree. C.
12. The method of claim 1, wherein the cooling includes cooling by
at least one of air and liquid.
13. The method of claim 1, wherein substantially all of the
iron-based composition in the cooling is transformed into a
martensite phase.
14. The method of claim 1, wherein the iron-based composition at
the end of cooling is substantially free of at least one phase
chosen from a ferrite phase and an austenite phase.
15. The method of claim 1, wherein the third temperature is between
about 650.degree. C. and about 780.degree. C.
16. The method of claim 1, wherein heat treating at the third
temperature includes heating the material to the third
temperature.
17. The method of claim 1, wherein heat treating at the third
temperature is carried out for between about 0.5 hours to about 3
hours.
18. The method of claim 1, wherein the third condition mitigates
formation of a ferrite phase of the iron-based composition.
19. The method of claim 1, further including cooling the material
from the third temperature to a fourth temperature lower than the
third temperature.
20. The method of claim 1, wherein heat treating at the third
temperature is carried out in a vertical furnace.
21. The method of claim 1, wherein at least some of the carbides
are thermally stable at a temperature of greater than or equal to
about 650.degree. C.
22. The method of claim 1, wherein at least some of the carbides
have a size of less than or equal to about 1 micron.
23. The method of claim 1, wherein at least some of the carbides
are homogeneously distributed within the martensite phase.
24. The method of claim 1, wherein the third temperature is lower
than the first temperature.
25. A method of making a composition, the method comprising:
subjecting a material to at least one of cold drawing, cold
rolling, and pilgering; heat treating the material including an
iron-based composition at a first temperature under a first
condition in which at least some of the iron-based composition is
transformed into an austenite phase; cooling the material to a
second temperature at a cooling rate under a second condition in
which at least some of the iron-based composition is transformed
into a martensite phase; and heat treating the material at a third
temperature under a third condition, in which carbides are
precipitated.
26. The method of claim 25, further including extruding an ingot
including the iron-based composition.
27. The method of claim 25, where subjecting includes intermediate
annealing the material.
28. The method of claim 25, where subjecting includes intermediate
annealing the material at a temperature below a transformation
temperature from a ferrite phase to an austenite phase.
29. The method of claim 25, further including forming an ingot
including the iron-based composition before the subjecting, wherein
the forming includes at least one process chosen from cold cathode
induction melting, vacuum induction melting, vacuum arc re-melting,
and electro-slag remelting.
30. The method of claim 25, further including forming an ingot
including the iron-based composition and purifying the ingot before
subjecting.
31. The method of claim 25, wherein subject further including
reducing a thickness of the material by at least 15%.
32. The method of claim 25, wherein the first condition mitigates
formation of a delta-ferrite phase of the iron-based
composition.
33. The method of claim 25, further including cooling the material
from the third temperature to a fourth temperature lower than the
third temperature.
34. The method of claim 25, further including cooling the material
from the third temperature to a fourth temperature that is about
20.degree. C.
35. The method of claim 25, wherein the composition is a part of a
fuel element, and the third temperatures is at about 700.degree.
C.
36. The method of claim 25, wherein the composition is a part of a
fuel duct, and the third temperatures is at about 650.degree.
C.
37. The method of claim 25, wherein the third temperature is lower
than the first temperature.
38. The method of claim 25, wherein the second temperature is about
20.degree. C.
39. The method of claim 25, wherein the iron-based composition
includes a steel.
40. The method of claim 25, wherein the iron-based composition
includes at least one element chosen from Cr, C, Mo, Ni, Mn, V, W,
Si, N, S, and P.
41-71. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/747,054, filed Dec. 28, 2012, which is
incorporated herein by reference in its entirety.
BACKGROUND
[0002] The present patent application relates to a fuel element
including a cladding material and methods related to same.
SUMMARY
[0003] Disclosed embodiments include fuel elements, fuel
assemblies, cladding materials, and methods of making and using
same.
[0004] The foregoing is a summary and thus may contain
simplifications, generalizations, inclusions, and/or omissions of
detail; consequently, those skilled in the art will appreciate that
the summary is illustrative only and is NOT intended to be in any
way limiting. In addition to any illustrative aspects, embodiments,
and features described above, further aspects, embodiments, and
features will become apparent by reference to the drawings and the
following detailed description. Other aspects, features, and
advantages of the devices and/or processes and/or other subject
matter described herein will become apparent in the teachings set
forth herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The skilled artisan will understand that the drawings
primarily are for illustrative purposes and are not intended to
limit the scope of the inventive subject matter described herein.
The drawings are not necessarily to scale; in some instances,
various aspects of the inventive subject matter disclosed herein
may be shown exaggerated or enlarged in the drawings to facilitate
an understanding of different features. In the drawings, like
reference characters generally refer to like features (e.g.,
functionally similar and/or structurally similar elements).
[0006] FIGS. 1a-1b provide partial-cutaway perspective views in
schematic form of an illustrative (a) nuclear fuel assembly and (b)
fuel element in one exemplary embodiment.
[0007] FIGS. 2a and 2b-2f, respectively, provide a flow chart of a
process of making a composition and illustrative details of the
process in one exemplary embodiment.
[0008] FIGS. 3a-3c provide optical micrographs showing the
different microstructures of iron-based compositions that have
undergone different processes in one exemplary embodiment.
[0009] FIGS. 4a and 4b-4e, respectively, provide a flow chart of a
process of making a composition and illustrative details of the
process in another exemplary embodiment.
[0010] FIGS. 5a and 5b, respectively, provide a flow chart of a
process of using a composition and illustrative details of the
process in one exemplary embodiment.
DETAILED DESCRIPTION
Introduction
[0011] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof. In the
drawings, the use of similar or the same symbols in different
drawings typically indicates similar or identical items, unless
context dictates otherwise.
[0012] The illustrative embodiments described in the detailed
description, drawings, and claims are not meant to be limiting.
Other embodiments may be utilized, and other changes may be made,
without departing from the spirit or scope of the subject matter
presented here.
[0013] One skilled in the art will recognize that the herein
described components (e.g., operations), devices, objects, and the
discussion accompanying them are used as examples for the sake of
conceptual clarity and that various configuration modifications are
contemplated. Consequently, as used herein, the specific exemplars
set forth and the accompanying discussion are intended to be
representative of their more general classes. In general, use of
any specific exemplar is intended to be representative of its
class, and the non-inclusion of specific components (e.g.,
operations), devices, and objects should not be taken as
limiting.
[0014] The present application uses formal outline headings for
clarity of presentation. However, it is to be understood that the
outline headings are for presentation purposes, and that different
types of subject matter may be discussed throughout the application
(e.g., device(s)/structure(s) may be described under
process(es)/operations heading(s) and/or process(es)/operations may
be discussed under structure(s)/process(es) headings; and/or
descriptions of single topics may span two or more topic headings).
Hence, the use of the formal outline headings is not intended to be
in any way limiting.
Overview
[0015] By way of overview, provided in one embodiment is a method
of making a composition, the method comprising: heat treating a
material including an iron-based composition at a first temperature
under a first condition in which at least some of the iron-based
composition is transformed into an austenite phase; cooling the
material to a second temperature at a cooling rate under a second
condition in which at least some of the iron-based composition is
transformed into a martensite phase; and heat treating the material
at a third temperature under a third condition in which carbides
are precipitated.
[0016] Provided in another embodiment is a method of making a
composition, the method comprising: subjecting a material to at
least one of cold drawing, cold rolling, and pilgering; heat
treating the material including an iron-based composition at a
first temperature under a first condition in which at least some of
the iron-based composition is transformed into an austenite phase;
cooling the material to a second temperature at a cooling rate
under a second condition in which at least some of the iron-based
composition is transformed into a martensite phase; and heat
treating the material at a third temperature under a third
condition, in which carbides are precipitated.
[0017] Provided in another embodiment is a composition comprising:
(Fe).sub.a(Cr).sub.b(M).sub.c; wherein a, b, and c are each a
number greater than zero representing a weight percentage; M is at
least one transition metal element; b is between 11 and 12; c is
between about 0.25 and about 0.9; and balanced by a; and the
composition further includes at least N at between about 0.01 wt %
and about 0.04 wt %.
[0018] Provided in another embodiment is a composition, comprising:
(Fe).sub.a(Cr).sub.b(Mo, Ni, Mn, W, V).sub.c; wherein a, b, and c
are each a number greater than zero representing a weight
percentage; b is between 11 and 12; c is between about 0.25 and
about 0.9; and balanced by a; at least substantially all of the
composition has a martensite phase; and the composition includes N
at between about 0.01 wt % and about 0.04 wt %.
[0019] Provided in another embodiment is a method of using a fuel
assembly, comprising: generating power using a fuel assembly, a
fuel element of which includes a composition, which is represented
by a chemical formula: (Fe).sub.a(Cr).sub.b(M)c; wherein a, b, and
c are each a number greater than zero representing a weight
percentage; M is at least one transition metal element; b is
between 11 and 12; c is between about 0.25 and about 0.9; and
balanced by a; and the composition further includes at least N at
between about 0.01 wt % and about 0.04 wt %.
[0020] Provided in another embodiment is a fuel element comprising
a tubular composition made by a method comprising: heat treating a
material including an iron-based composition at a first temperature
under a first condition in which at least some of the iron-based
composition is transformed into an austenite phase; cooling the
material to a second temperature at a cooling rate under a second
condition in which at least some of the iron-based composition is
transformed into a martensite phase; and heat treating the material
at a third temperature under a third condition, in which carbides
are precipitated. In one embodiment, in compositions where nitrogen
is present, the precipitation of carbides may be accompanied by
precipitation of nitrides and carbonitrides.
Fuel Assembly
[0021] FIG. 1a provides a partial illustration of a nuclear fuel
assembly 10 in accordance with one embodiment. The fuel assembly
may be a fissile nuclear fuel assembly or a fertile nuclear fuel
assembly. The assembly may include fuel elements (or "fuel rods" or
"fuel pins") 11. FIG. 1b provides a partial illustration of a fuel
element 11 in accordance with one embodiment. As shown in this
embodiment, the fuel element 11 may include a cladding material 13,
a fuel 14, and, in some instances, at least one gap 15.
[0022] Fuel may be sealed within a cavity by the exterior cladding
material 13. In some instances, the multiple fuel materials may be
stacked axially as shown in FIG. 1b, but this need not be the case.
For example, a fuel element may contain only one fuel material. In
one embodiment, gap(s) 15 may be present between the fuel material
and the cladding material, though gap(s) need not be present. In
one embodiment, the gap is filled with a pressurized atmosphere,
such as a pressured helium atmosphere.
[0023] A fuel may contain any fissionable material. A fissionable
material may contain a metal and/or metal alloy. In one embodiment,
the fuel may be a metal fuel. It can be appreciated that metal fuel
may offer relatively high heavy metal loadings and excellent
neutron economy, which is desirable for breed-and-burn process of a
nuclear fission reactor. Depending on the application, fuel may
include at least one element chosen from U, Th, Am, Np, and Pu. The
term "element" as represented by a chemical symbol herein may refer
to one that is found in the Periodic Table--this is not to be
confused with the "element" of a "fuel element". In one embodiment,
the fuel may include at least about 90 wt % U--e.g., at least 95 wt
%, 98 wt %, 99 wt %, 99.5 wt %, 99.9 wt %, 99.99 wt %, or higher of
U. The fuel may further include a refractory material, which may
include at least one element chosen from Nb, Mo, Ta, W, Re, Zr, V,
Ti, Cr, Ru, Rh, Os, Ir, and Hf. In one embodiment, the fuel may
include additional burnable poisons, such as boron, gadolinium, or
indium.
[0024] The metal fuel may be alloyed with about 3 wt % to about 10
wt % zirconium to stabilize dimensionally the alloy during
irradiation and to inhibit low-temperature eutectic and corrosion
damage of the cladding. A sodium thermal bond fills the gap that
exists between the alloy fuel and the inner wall of the cladding
tube to allow for fuel swelling and to provide efficient heat
transfer, which may keep the fuel temperatures low. In one
embodiment, individual fuel elements 11 may have a thin wire 12
from about 0.8 mm diameter to about 1.6 mm diameter helically
wrapped around the circumference of the clad tubing to provide
coolant space and mechanical separation of individual fuel elements
56 within the housing of the fuel assemblies 18 and 20 (that also
serve as the coolant duct). In one embodiment, the cladding 13,
and/or wire wrap 12 may be fabricated from ferritic-martensitic
steel because of its irradiation performance as indicated by a body
of empirical data.
Fuel Element
[0025] A "fuel element", such as element 11 shown in FIGS. 1a-1b,
in a fuel assembly of a power generating reactor may generally take
the form of a cylindrical rod. The fuel element may be a part of a
power generating reactor, which is a part of a nuclear power plant.
Depending on the application, the fuel element may have any
suitable dimensions with respect to its length and diameter. The
fuel element may include a cladding layer 13 and a fuel 14 disposed
interior to the cladding layer 13. In the case of a nuclear
reactor, the fuel may contain (or be) a nuclear fuel. In one
embodiment, the nuclear fuel may be an annular nuclear fuel. The
fuel element may additionally include a liner disposed between the
nuclear fuel 14 and the cladding layer 13. The liner may contain
multiple layers.
[0026] The fuel may have any geometry. In one embodiment, the fuel
has an annular geometry. In such an embodiment, a fuel in an
annular form may allow a desirable level of fuel density to be
achieved after a certain level of burn-up. Also, such an annular
configuration may maintain compressive forces between the fuel and
the cladding to promote thermal transport. The fuel may be tailored
to have various properties, depending on the application. For
example, the fuel may have any level of density. In one embodiment,
it is desirable to have a high density of fuel, such as one as
close to theoretical density uranium (in the case of a fuel
containing uranium) as possible. In another embodiment, having a
high porosity (low density) may prevent formation of additional
internal voids during irradiation, decreasing fuel pressure on
structural material, such as cladding, during operation of the
nuclear fuel.
[0027] The cladding material for the cladding layer 13 may include
any suitable material, depending on the application. In one
embodiment, the cladding layer 13 may include at least one material
chosen from a metal, a metal alloy, and a ceramic. In one
embodiment, the cladding layer 13 may contain a refractory
material, such as a refractory metal including at least one element
chosen from Nb, Mo, Ta, W, Re, Zr, V, Ti, Cr, Ru, Rh, Os, Ir, Nd,
and Hf. In another embodiment, the cladding material may be chosen
from a ceramic material, such as silicon carbide or aluminum oxide
(alumina).
[0028] A metal alloy in cladding layer 13 may be, in one exemplary
embodiment, steel. The steel may be chosen from an austenitic
steel, a ferritic-martensitic steel, an oxide-dispersed steel, T91
steel, T92 steel, HT9 steel, 316 steel, and 304 steel. The steel
may have any type of microstructure. For example, the steel may
include at least one of a martensite phase, a ferrite phase, and an
austenite phase. In one embodiment, substantially all of the steel
has at least one phase chosen from a martensite phase, a ferrite
phase, and an austenite phase. Depending on the application, the
microstructure may be tailored to have a particular phase (or
phases). The cladding layer 13 may include an iron-based
composition as described below.
[0029] At least some of the components of the fuel elements may be
bonded. The bonding may be physical (e.g., mechanical) or chemical.
In one embodiment, the nuclear fuel and the cladding are
mechanically bonded. In one embodiment, the first layer and the
second layer are mechanically bonded.
Iron-Based Composition
[0030] Provided in one embodiment herein is a composition including
a metal. The metal may include at least one of a metal, metal
alloy, and intermetallic composition. In one embodiment, the metal
includes iron. In one embodiment, the composition includes an
iron-based composition. The term "X-based" composition in one
embodiment may refer to a composition including a significant
amount an element X (e.g., metal element). The amount may be, for
example, at least 30%--e.g., at least 40%, at least 50%, at least
60%, at least 70%, at least 80%, at least 90%, at least 95%, at
least 99%, or more. The percentage herein may refer to weight
percent or a volume (or atomic) percent, depending on the context.
In one embodiment, the iron-based composition may include
steel.
[0031] The compositions described herein may be employed as a
component of a nuclear fuel element, such as the cladding material
thereof. However, the metal-containing composition need not be
limited to cladding material and may be employed wherever such a
composition is employed. For example, provided in one embodiment is
a composition that is represented by the chemical formula
(Fe).sub.a(Cr).sub.b(M).sub.c, wherein a, b, and c are each a
number greater than zero representing a weight percentage;
depending on the context, these numbers may alternatively represent
a volume percentage. In one embodiment, b is a number between 11
and 12, c is between about 0.25 and about 0.9; balanced by a. In
one embodiment, the composition includes at least nitrogen ("N") at
between about 0.005 wt % and about 0.05 wt %--e.g., about 0.01 wt %
and about 0.04 wt %, between about 0.01 wt % and about 0.03 wt %,
between about 0.02 wt % and about 0.03 wt %, etc. The element M may
represent at least one transition metal element. The element M in
this iron-based composition may be any transition metal element
found in the Periodic Table--e.g., the elements in Groups 3-12 of
the Periodic Table. In one embodiment, M represents at least one of
Mo, Ni, Mn, W, and V.
[0032] In another embodiment, the composition may include (or be)
an iron-based composition including a steel composition. The
composition may be represented by the chemical formula:
(Fe).sub.a(Cr).sub.b(Mo, Ni, Mn, W, V).sub.c, wherein a, b, and c
are each a number greater than zero representing a weight
percentage; depending on the context, the numbers may alternatively
represent a volume percentage. In one embodiment, the number b is
between 11 and 12; c is between about 0.25 and about 0.9; balanced
by a. In one embodiment, the composition includes N at between
about 0.01 wt % and about 0.04 wt %.
[0033] The composition may contain at least one additional element.
The additional element may be a non-metal element. In one
embodiment, the non-metal element may be at least one element
chosen from Si, S, C, and P. The additional element may be a metal
element, including Cu, Cr, Mo, Mn, V, W, Ni, etc. In one
embodiment, the composition further includes Cr at between about 10
wt % and about 12.5 wt %; C at between about 0.17 wt % and about
0.22 wt %; Mo at between about 0.80 wt % and about 1.2 wt %; Si
less than or equal to about 0.5 wt %; Mn less than or equal to
about 1.0 wt %; V at between about 0.25 wt % and about 0.35 wt %; W
at between about 0.40 wt % and about 0.60 wt %; P less than or
equal to about 0.03 wt %; and S less than or equal to about 0.3 wt
%. In another embodiment, the composition further includes Ni at
between about 0.3 wt % and 0.7 wt %. In another embodiment, the
composition further includes Cr at about 11.5 wt %; C at about 0.20
wt %; Mo at about 0.90 wt %; Ni at about 0.55 wt %; Mn at about
0.65 wt %; V at about 0.30 wt %; W at about 0.50 wt %; Si at about
0.20 wt % and N at about 0.02 wt %. Other elements may also be
present in any suitable amount. In some cases, certain incidental
impurities may be present.
[0034] The composition may include an iron-based composition that
includes a steel composition including a tailored microstructure.
For example, the compositions provided herein may have a small
amount of a delta-ferrite phase. In one embodiment, the composition
is at least substantially free of delta-ferrite. In another
embodiment, the composition is completely free of delta-ferrite.
Instead of a ferrite phase, the composition may include a
martensite phase (e.g., tempered martensite). In one embodiment,
substantially all of the composition has a martensite phase. In
another embodiment, completely all of the composition has a
martensite phase. As described below, one technique of tailoring
the microstructure (e.g., to mitigate formation of a ferrite phase)
may be to control the content of nitrogen within the range provided
herein. Mitigation herein may refer to reduction and/or prevention
but need not refer to total elimination.
[0035] The microstructure, including the phases, may be described
in terms of a chromium equivalent. In one embodiment, chromium
equivalent ("Cr.sub.eq") is the sum of ferrite forming elements
plotted in constitution diagrams for the estimation of phases in
stainless steel, weld metal, and calculated from various equations.
In some instances, chromium equivalent may be used in conjunction
with nickel equivalent, which is the sum of austenite forming
elements. The equation may be any suitable equation, depending at
least on the material chemistry. In one embodiment, the equation
may be represented by the net chromium equivalent, net Cr.sub.eq.
which is the difference between chromium equivalent and nickel
equivalent. Net Cr.sub.eq (wt %)=(% Cr)+6(% Si)+4(% Mo)+11(% V)+5(%
Nb)+1.5(% W)+8(% Ti)+12(% Al)-4(% Ni)-2(% Co)-2(% Mn)-(% Cu)-40(%
C)-30(% N). In one embodiment, the compositions described herein
may have Cr.sub.eq of less than or equal to about 10--e.g., less
than or equal to about 9, 8, 7, 6, 5, 4, 3, 2, or less. In one
embodiment, the Cr.sub.eq may be kept under 9 to mitigate formation
of ferrites. Based on the equation above, N-content may play an
important role in the value of Cr.sub.eq, and hence the ferrite
formation (or lack thereof).
[0036] Due at least in part to the microstructure, the compositions
described herein may have tailored material properties. For
example, the compositions may have a high thermal stability.
Thermal stability of a composition in one embodiment may refer to
the resistance of a particular phase of the composition to
decomposition (or dissociation) into another phase at an elevated
temperature. In one embodiment, the compositions described herein
are substantially thermally stable at a temperature of greater or
equal to about 500.degree. C.--e.g., greater or equal to about
550.degree. C., about 600.degree. C., or higher.
[0037] The compositions provided herein may include additional
phase(s) or material(s). For example, in a case where the
composition includes carbon, the carbon element may be present in
the form of a carbide. In one embodiment, the composition may
include carbides distributed substantially uniformly in the
composition. The carbides may have any suitable sizes, depending on
the application. In one embodiment, the carbides have a size of
less than or equal to about 2 microns--e.g., less than or equal to
about 1 micron, 0.5 microns, 0.2 microns, 0.1 microns, or
smaller.
Methods of Making/Using the Iron-Based Composition
[0038] The iron-based composition and a fuel element including the
composition described herein may be manufactured by a variety of
techniques. The iron-based composition may be any of the
compositions described herein. For example, the composition may
include a steel. Provided in another embodiment is a fuel element
having a tubular structure made by the methods described herein.
For example, referring to FIG. 2a, provided in one embodiment is a
method of making a composition; the method includes heat treating a
material including an iron-based composition at a first temperature
under a first condition in which at least some of the iron-based
composition is transformed into an austenite phase (step 201);
cooling the material to a second temperature at a cooling rate
under a second condition in which at least some of the iron-based
composition is transformed into a martensite phase (step 202); and
heat treating the material at a third temperature under a third
condition in which carbides are precipitated (step 203). In one
embodiment, steps 201 and 202 together may be referred to as
normalization, whereas step 203 may be referred to as
tempering.
[0039] The first temperature may be any temperature suitable for
the first condition. In one example, the first temperature may be
above the austenitization temperature of the composition--the
temperature at which substantially all of the ferrite phase of the
iron-based composition transforms to an austenite phase. The
austenite temperature varies with the material chemistry. In one
embodiment, the first temperature is between about 900.degree. C.
and about 1200.degree. C.--e.g., about 1000.degree. C. and about
1150.degree. C., about 1025.degree. C. and about 1100.degree. C.,
etc. The first temperature may be higher than 1200.degree. C. or
lower than 900.degree. C., depending on the material.
[0040] Referring to FIG. 2b, the process of heat treating at the
first temperature may further comprise heating the material to the
first temperature (step 204). Heat treating at the first
temperature may be carried out for any suitable length of time,
depending on the material involved. The time may be adjusted such
that the length is sufficiently long to promote formation of a
homogeneous austenite solid solution. In one embodiment, the heat
treatment may be carried out for about at least 3 minutes--e.g., at
least 4 minutes, 5 minutes, 15 minutes, 20 minutes, 30 minutes, 60
minutes, 90 minutes, 120 minutes, 150 minutes, 180 minutes, or
more. A longer or shorter length of time is also possible. In one
embodiment, heat treating at the first temperature may be carried
out for between about 1 minute and about 200 minutes--e.g., about 2
minutes and about 150 minutes, about 3 minutes and about 120
minutes, about 5 minutes and about 60 minutes, etc. In one
embodiment, during heat treating at the first temperature (e.g. at
the end of the treatment), at least some of the iron-based
composition is transformed into an austenite phase. In one
embodiment, substantially all of the composition is transformed
into an austenite phase. In another embodiment, completely all of
the composition is transformed into an austenite phase. In one
embodiment, the first condition mitigates formation of a
delta-ferrite phase of the iron-based composition. In another
embodiment, the first condition promotes transformation of
substantially all of the iron-based composition into an austenite
phase.
[0041] Referring to FIG. 2c, the process of heat treating at the
first temperature (step 201) may further comprise dissolving at
least substantially all of the carbides, if any, present in the
iron-based composition of the material (step 205).
[0042] The second temperature in step 202 may be any temperature
suitable for the second condition. In one embodiment, the second
temperature is less than or equal to 60.degree. C.--e.g., less than
or equal to 50.degree. C., 40.degree. C., 30.degree. C., 20.degree.
C., 10.degree. C., or less. In one embodiment, the third
temperature is about room temperature (e.g., 20.degree. C.).
Cooling may be carried out via any suitable techniques. In one
embodiment, cooling includes cooling by at least one of air and
liquid. In one embodiment, the second condition promotes
transformation of substantially all of the iron-based composition
into a martensite phase. For example, the cooling may be carried
out at a sufficient rate such that during cooling (e.g. at the end
of the treatment), at least some of the iron-based composition is
transformed into a martensite phase. In one embodiment, the rate is
high enough that substantially all of the composition is
transformed into a martensite phase. In another embodiment, the
rate is high enough that completely all of the composition is
transformed into a martensite phase. In one embodiment, at the end
of cooling the composition is substantially free of at least one
phase chosen from a ferrite phase and an austenite phase. In one
embodiment, at the end of cooling the composition is completely
free of at least one phase chosen from a ferrite phase and an
austenite phase.
[0043] The third temperature in step 203 may be any temperature
suitable for the third condition. The third temperatures may be
lower than the temperature above which austenite begins to form. In
one embodiment, the third temperature may be lower than the first
temperature. In one embodiment, the third temperature is at least
500.degree. C.--e.g., at least 550.degree. C., 600.degree. C.,
650.degree. C., 700.degree. C., 750.degree. C., 800.degree. C.,
850.degree. C., 900.degree. C., or more. In one embodiment, the
third temperature is between about 500.degree. C. and about
900.degree. C.--e.g., about 550.degree. C. and about 850.degree.
C., about 600.degree. C. and about 800.degree. C., about
650.degree. C. and about 780.degree. C., about 700.degree. C. and
about 750.degree. C., etc. A higher or lower temperature is also
possible. The third temperature may be high enough to precipitate
carbides and impart high temperature stability of carbides but low
enough that carbide density is high and the carbide size is small
with a homogeneous distribution of carbides for void swelling
resistance.
[0044] Referring to FIG. 2d, heat treating at the third temperature
may include heating the material to the third temperature (step
206). Heat treating at the third temperature may be carried out for
any suitable length of time, depending on the material involved. In
one embodiment, heat treating at the third temperature may be
carried out for between about 0.1 hours and about 5 hours--e.g.,
between about 0.2 hours to about 4 hours, about 0.5 hours to about
3 hours, about 1 hours and about 2 hours, etc. A longer or shorter
length of time is also possible. In one embodiment, the third
condition may mitigate the formation of a ferrite phase and/or an
austenite phase of the iron-based composition. In one embodiment,
the composition is substantially free of a ferrite phase and/or an
austenite phase. The heat treatment may be carried out by any
suitable techniques. In one embodiment, heat treating at the third
temperature is carried out in a vertical furnace.
[0045] Additional process(es) may be involved. For example,
referring to FIG. 2e, the method may further comprise cooling the
composition from the third temperature to a fourth temperature
(step 207). The fourth temperature may be lower than the third
temperatures. For example, the fourth temperature may less than or
equal to 60.degree. C.--e.g., less than or equal to 50.degree. C.,
40.degree. C., 30.degree. C., 20.degree. C., 10.degree. C., or
less. In one embodiment, the fourth temperature is about room
temperature (e.g., 20.degree. C.). Referring to FIG. 2f, the method
may further comprise controlling the wt % of N in the iron-based
composition of the material to mitigate growth of a carbide phase
of the iron-based composition (step 208).
[0046] Referring to FIGS. 3a-3c, the differences in microstructure
of the iron-based composition are illustrated in the figures. FIG.
3a shows a microstructure with blocky delta ferrite grains, loss of
tempered martensite microstructure, and many grains devoid of
complex carbide microstructure, in conventional steel. FIG. 3b
shows an improved microstructure, with more homogenous carbide
microstructure in the tempered martensite grains--note there are
still some small delta ferrite grains in the microstructure. FIG.
3c shows a result of subjecting a steel sample to the processes
described herein. The figure shows improved microstructure
substantially free of delta ferrite with most grain regions having
a high density of finely distributed carbides.
[0047] Another embodiment provides an alternative method of making
of a composition. Referring to FIG. 4a, the method includes:
subjecting a material to at least one of cold drawing, cold
rolling, and pilgering (step 401); heat treating the material
including an iron-based composition at a first temperature under a
first condition in which at least some of the iron-based
composition is transformed into an austenite phase (step 402);
cooling the material to a second temperature at a cooling rate
under a second condition in which at least some of the iron-based
composition is transformed into a martensite phase (step 403); and
heat treating the material at a third temperature under a third
condition, in which carbides are precipitated (step 404).
[0048] In step 401, the material is cold worked; cold drawing, cold
rolling, and pilgering are only some examples of processes that the
material may be subjected to. One result of cold working is that
the material dimension may be changed to a desired value. For
example, the thickness of the material may be reduced as a result
of cold working In one embodiment, the reduction in thickness may
be, for example, by at least 5%--e.g., at least 10%, 15%, 20%, 25%,
or more. In one embodiment, the reduction is between about 5% and
about 20%--e.g., between about 8% and about 16%, between about 10%
and about 15%, etc. Higher or lower values are also possible.
[0049] The dimension(s) of the material may be controlled via
additional processes. In one embodiment, the ingot may undergo a
thermo-mechanical processing to form the material with the final
desired dimension(s). Referring to FIG. 4b, the starting material
to be processed may be a billet, ingot, forging, etc., that has a
cylindrical shape (step 405). The starting material is then
mechanically worked (e.g., cold worked) by suitable
tube-manufacturing process(es) (step 406). When the
tube-manufacturing process involves cold work, the work piece may
be annealed ("intermediate annealing") after the working process at
a temperature below the temperature above which austenite begins to
form--below a transformation temperature from ferrite phase to an
austenite phase (step 407). In one embodiment, austenite needs to
be avoided because it would transform on cooling to hard
martensite, thus counteracting the softening process. Steps 406 and
407 are repeated until the final dimensions are achieved. In one
embodiment, after the final cold working step that provides the
tube with its final dimensions, the tube is not annealed again. The
tube then may undergo normalization and tempering, as described
above.
[0050] The method may include additional processes. Referring to
FIG. 4c, the method may further comprise extruding an ingot
including the composition (step 409). Referring to FIG. 4d, the
method may further comprise forming an ingot including the
iron-based composition before the subjecting step, wherein the
forming includes at least one process chosen from cold cathode
induction melting, vacuum induction melting, vacuum arc re-melting,
and electro-slag remelting (step 410). Referring to FIG. 4e, the
method may further comprise forming an ingot including the
iron-based composition and purifying the ingot to remove impurities
(e.g., P, S, etc.) before the subjecting step (step 411). The
forming and the purifying processes may involve any suitable
techniques. The aforedescribed temperatures may vary depending on
the materials and/or applications thereof involved.
[0051] A fuel element (and fuel assemblies) including the
composition (e.g., as the cladding) may be used in a variety of
applications. Provided in one embodiment is a method of using a
fuel assembly. Referring to FIG. 5a, the method includes generating
power using a fuel assembly, a fuel element of which includes any
of the iron-based compositions described herein (step 501).
Referring to FIG. 5b, the generation of power may include
generating at least one of electrical power and thermal power (step
5b).
[0052] Power Generation
[0053] As described above, the fuel assemblies described herein may
be a part of a power or energy generator, which may be a part of a
power generating plant. The fuel assembly may be a nuclear fuel
assembly. In one embodiment, the fuel assembly may include a fuel,
a plurality of fuel elements, and a plurality of fuel ducts, such
as those described above. The fuel ducts may include the plurality
of fuel elements disposed therein.
[0054] The fuel assembly described herein may be adapted to produce
a peak areal power density of at least about 50 MW/m.sup.2--e.g.,
at least about 60 MW/m.sup.2, about 70 MW/m.sup.2, about 80
MW/m.sup.2, about 90 MW/m.sup.2, about 100 MW/m.sup.2, or higher.
In some embodiments, the fuel assembly may be subjected to
radiation damage at a level of at least about 120 displacements per
atom ("DPA")--e.g., at least about 150 DPA, about 160 DPA, about
180 DPA, about 200 DPA, or higher.
[0055] All of the above U.S. patents, U.S. patent application
publications, U.S. patent applications, foreign patents, foreign
patent applications and non-patent publications referred to in this
specification and/or listed in any Application Data Sheet, are
incorporated herein by reference in their entirety, to the extent
not inconsistent herewith. In the event that one or more of the
incorporated literature and similar materials differs from or
contradicts this application, including but not limited to defined
terms, term usage, described techniques, or the like, this
application controls.
[0056] With respect to the use of substantially any plural and/or
singular terms herein, those having skill in the art can translate
from the plural to the singular and/or from the singular to the
plural as is appropriate to the context and/or application. The
various singular/plural permutations are not expressly set forth
herein for sake of clarity.
[0057] The herein described subject matter sometimes illustrates
different components contained within, or connected with, different
other components. It is to be understood that such depicted
architectures are merely exemplary, and that in fact many other
architectures may be implemented which achieve the same
functionality. In a conceptual sense, any arrangement of components
to achieve the same functionality is effectively "associated" such
that the desired functionality is achieved. Hence, any two
components herein combined to achieve a particular functionality
can be seen as "associated with" each other such that the desired
functionality is achieved, irrespective of architectures or
intermedial components. Likewise, any two components so associated
can also be viewed as being "operably connected," or "operably
coupled," to each other to achieve the desired functionality, and
any two components capable of being so associated can also be
viewed as being "operably couplable," to each other to achieve the
desired functionality. Specific examples of operably couplable
include, but are not limited to, physically mateable and/or
physically interacting components, and/or wirelessly interactable,
and/or wirelessly interacting components, and/or logically
interacting, and/or logically interactable components.
[0058] In some instances, one or more components may be referred to
herein as "configured to," "configured by," "configurable to,"
"operable/operative to," "adapted/adaptable," "able to,"
"conformable/conformed to," etc. Those skilled in the art will
recognize that such terms (e.g. "configured to") can generally
encompass active-state components and/or inactive-state components
and/or standby-state components, unless context requires
otherwise.
[0059] While particular aspects of the present subject matter
described herein have been shown and described, it will be apparent
to those skilled in the art that, based upon the teachings herein,
changes and modifications may be made without departing from the
subject matter described herein and its broader aspects and,
therefore, the appended claims are to encompass within their scope
all such changes and modifications as are within the true spirit
and scope of the subject matter described herein. It will be
understood by those within the art that, in general, terms used
herein, and especially in the appended claims (e.g., bodies of the
appended claims) are generally intended as "open" terms (e.g., the
term "including" should be interpreted as "including but not
limited to," the term "having" should be interpreted as "having at
least," the term "includes" should be interpreted as "includes but
is not limited to," etc.). It will be further understood by those
within the art that if a specific number of an introduced claim
recitation is intended, such an intent will be explicitly recited
in the claim, and in the absence of such recitation no such intent
is present. For example, as an aid to understanding, the following
appended claims may contain usage of the introductory phrases "at
least one" and "one or more" to introduce claim recitations.
However, the use of such phrases should not be construed to imply
that the introduction of a claim recitation by the indefinite
articles "a" or "an" limits any particular claim containing such
introduced claim recitation to claims containing only one such
recitation, even when the same claim includes the introductory
phrases "one or more" or "at least one" and indefinite articles
such as "a" or "an" (e.g., "a" and/or "an" should typically be
interpreted to mean "at least one" or "one or more"); the same
holds true for the use of definite articles used to introduce claim
recitations. In addition, even if a specific number of an
introduced claim recitation is explicitly recited, those skilled in
the art will recognize that such recitation should typically be
interpreted to mean at least the recited number (e.g., the bare
recitation of "two recitations," without other modifiers, typically
means at least two recitations, or two or more recitations).
Furthermore, in those instances where a convention analogous to "at
least one of A, B, and C, etc." is used, in general such a
construction is intended in the sense one having skill in the art
would understand the convention (e.g., "a system having at least
one of A, B, and C" would include but not be limited to systems
that have A alone, B alone, C alone, A and B together, A and C
together, B and C together, and/or A, B, and C together, etc.). In
those instances where a convention analogous to "at least one of A,
B, or C, etc." is used, in general such a construction is intended
in the sense one having skill in the art would understand the
convention (e.g., "a system having at least one of A, B, or C"
would include but not be limited to systems that have A alone, B
alone, C alone, A and B together, A and C together, B and C
together, and/or A, B, and C together, etc.). It will be further
understood by those within the art that typically a disjunctive
word and/or phrase presenting two or more alternative terms,
whether in the description, claims, or drawings, should be
understood to contemplate the possibilities of including one of the
terms, either of the terms, or both terms unless context dictates
otherwise. For example, the phrase "A or B" will be typically
understood to include the possibilities of "A" or "B" or "A and
B."
[0060] With respect to the appended claims, those skilled in the
art will appreciate that recited operations therein may generally
be performed in any order. Also, although various operational flows
are presented in a sequence(s), it should be understood that the
various operations may be performed in other orders than those
which are illustrated, or may be performed concurrently. Examples
of such alternate orderings may include overlapping, interleaved,
interrupted, reordered, incremental, preparatory, supplemental,
simultaneous, reverse, or other variant orderings, unless context
dictates otherwise. Furthermore, terms like "responsive to,"
"related to," or other past-tense adjectives are generally not
intended to exclude such variants, unless context dictates
otherwise.
[0061] Those skilled in the art will appreciate that the foregoing
specific exemplary processes and/or devices and/or technologies are
representative of more general processes and/or devices and/or
technologies taught elsewhere herein, such as in the claims filed
herewith and/or elsewhere in the present application.
[0062] While various aspects and embodiments have been disclosed
herein, other aspects and embodiments will be apparent to those
skilled in the art. The various aspects and embodiments disclosed
herein are for purposes of illustration and are not intended to be
limiting, with the true scope and spirit being indicated by the
following claims.
[0063] Any portion of the processes described herein may be
automated. The automation may be accomplished by involving at least
one computer. The automation may be executed by program that is
stored in at least one non-transitory computer readable medium. The
medium may be, for example, a CD, DVD, USB, hard drive, etc. The
selection and/or design of the fuel element structure, including
the assembly, may also be optimized by using the computer and/or a
software program.
[0064] The above-described embodiments of the invention can be
implemented in any of numerous ways. For example, some embodiments
may be implemented using hardware, software or a combination
thereof. When any aspect of an embodiment is implemented at least
in part in software, the software code can be executed on any
suitable processor or collection of processors, whether provided in
a single computer or distributed among multiple computers.
[0065] Also, the technology described herein may be embodied as a
method, of which at least one example has been provided. The acts
performed as part of the method may be ordered in any suitable way.
Accordingly, embodiments may be constructed in which acts are
performed in any order different from that illustrated, which may
include performing some acts simultaneously, even though shown as
sequential acts in illustrative embodiments.
[0066] All definitions, as defined and used herein, should be
understood to control over dictionary definitions, definitions in
documents incorporated by reference, and/or ordinary meanings of
the defined terms.
[0067] The indefinite articles "a" and "an," as used herein in the
specification and in the claims, unless clearly indicated to the
contrary, should be understood to mean "at least one."
[0068] The phrase "and/or," as used herein in the specification and
in the claims, should be understood to mean "either or both" of the
elements so conjoined, i.e., elements that are conjunctively
present in some cases and disjunctively present in other cases.
Multiple elements listed with "and/or" should be construed in the
same fashion, i.e., "one or more" of the elements so conjoined.
Other elements may optionally be present other than the elements
specifically identified by the "and/or" clause, whether related or
unrelated to those elements specifically identified. Thus, as a
non-limiting example, a reference to "A and/or B", when used in
conjunction with open-ended language such as "including" can refer,
in one embodiment, to A only (optionally including elements other
than B); in another embodiment, to B only (optionally including
elements other than A); in yet another embodiment, to both A and B
(optionally including other elements); etc.
[0069] As used herein in the specification and in the claims, "or"
should be understood to have the same meaning as "and/or" as
defined above. For example, when separating items in a list, "or"
or "and/or" shall be interpreted as being inclusive, i.e., the
inclusion of at least one, but also including more than one, of a
number or list of elements, and, optionally, additional unlisted
items. Only terms clearly indicated to the contrary, such as "only
one of or "exactly one of," or, when used in the claims,
"consisting of," will refer to the inclusion of exactly one element
of a number or list of elements. In general, the term "or" as used
herein shall only be interpreted as indicating exclusive
alternatives (i.e. "one or the other but not both") when preceded
by terms of exclusivity, such as "either," "one of," "only one of,"
or "exactly one of" "Consisting essentially of," when used in the
claims, shall have its ordinary meaning as used in the field of
patent law.
[0070] As used herein in the specification and in the claims, the
phrase "at least one," in reference to a list of one or more
elements, should be understood to mean at least one element
selected from any one or more of the elements in the list of
elements, but not necessarily including at least one of each and
every element specifically listed within the list of elements and
not excluding any combinations of elements in the list of elements.
This definition also allows that elements may optionally be present
other than the elements specifically identified within the list of
elements to which the phrase "at least one" refers, whether related
or unrelated to those elements specifically identified. Thus, as a
non-limiting example, "at least one of A and B" (or, equivalently,
"at least one of A or B," or, equivalently "at least one of A
and/or B") can refer, in one embodiment, to at least one,
optionally including more than one, A, with no B present (and
optionally including elements other than B); in another embodiment,
to at least one, optionally including more than one, B, with no A
present (and optionally including elements other than A); in yet
another embodiment, to at least one, optionally including more than
one, A, and at least one, optionally including more than one, B
(and optionally including other elements); etc.
[0071] Any ranges cited herein are inclusive. The terms
"substantially" and "about" used throughout this Specification are
used to describe and account for small fluctuations. For example,
they can refer to less than or equal to .+-.5%, such as less than
or equal to .+-.2%, such as less than or equal to .+-.1%, such as
less than or equal to .+-.0.5%, such as less than or equal to
.+-.0.2%, such as less than or equal to .+-.0.1%, such as less than
or equal to .+-.0.05%.
[0072] In the claims, as well as in the specification above, all
transitional phrases such as "including," "carrying," "having,"
"containing," "involving," "holding," "composed of," and the like
are to be understood to be open-ended, i.e., to mean including but
not limited to. Only the transitional phrases "consisting of and
"consisting essentially of" shall be closed or semi-closed
transitional phrases, respectively, as set forth in the United
States Patent Office Manual of Patent Examining Procedures, Section
2111.03.
[0073] The claims should not be read as limited to the described
order or elements unless stated to that effect. It should be
understood that various changes in form and detail may be made by
one of ordinary skill in the art without departing from the spirit
and scope of the appended claims. All embodiments that come within
the spirit and scope of the following claims and equivalents
thereto are claimed.
* * * * *